﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace transferEncoding
{
    class Program
    {
        static void Main(string[] args)
        {
            Encoding originEncod = null;
            Encoding targetEncod = null;

            if (args.Count() == 0 || args[0].Contains("help"))
            {
                Console.WriteLine("第一个参数为输入文件绝对路径 第二个参数为输出文件绝对路径 第三个参数为指定编码 第四个参数为指定命令参考如下");
                Console.WriteLine("-h 强制转换");
                return;
            }

            if ((args[0] == args[1] && args.Count() < 4) || (args[0] == args[1] && args.Count() >= 4 && args[3] != "-h"))
            {
                Console.WriteLine("输入文件与输出文件相同,如需强制转换请在第4个参数加上 -h");
                return;
            }

            try
            {
                targetEncod = Encoding.GetEncoding(args[2].ToUpper());
                //   Encoding.GetEncoding("UTF-8");
                // Console.WriteLine("编码正确");
            }
            catch
            {
                Console.WriteLine("\"" + args[2].ToUpper() + "\"");
                Console.WriteLine("指定编码格式错误");
            }

            try
            {
                originEncod = GetType(args[0]);
                // Console.WriteLine("获取编码类型正常");
            }
            catch
            {
                Console.WriteLine("文件路径错误");
            }

            try
            {
                var buffer = File.ReadAllBytes(args[0]);
                buffer = Encoding.Convert(originEncod, targetEncod, buffer);
                File.WriteAllBytes(args[1], buffer);
                Console.WriteLine("转换完成");

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            return;



            //var buffer = File.ReadAllBytes(@"F:\OpenDataFTP\DataAutomation\DailySem.csv");
            //buffer = Encoding.Convert(Encoding.GetEncoding("GB2312"), Encoding.UTF8, buffer);
            //File.WriteAllBytes(@"F:\OpenDataFTP\DataAutomation\DailySem2.csv", buffer);

        }


        /// <summary> 
        /// 给定文件的路径，读取文件的二进制数据，判断文件的编码类型 
        /// </summary> 
        /// <param name="FILE_NAME">文件路径</param> 
        /// <returns>文件的编码类型</returns> 
        public static System.Text.Encoding GetType(string FILE_NAME)
        {
            FileStream fs = new FileStream(FILE_NAME, FileMode.Open, FileAccess.Read);
            Encoding r = GetType(fs);
            fs.Close();
            return r;
        }

        /// <summary> 
        /// 通过给定的文件流，判断文件的编码类型 
        /// </summary> 
        /// <param name="fs">文件流</param> 
        /// <returns>文件的编码类型</returns> 
        public static System.Text.Encoding GetType(FileStream fs)
        {
            byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };
            byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };
            byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //带BOM 
            Encoding reVal = Encoding.Default;

            BinaryReader r = new BinaryReader(fs, System.Text.Encoding.Default);
            int i;
            int.TryParse(fs.Length.ToString(), out i);
            byte[] ss = r.ReadBytes(i);
            if (IsUTF8Bytes(ss) || (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF))
            {
                reVal = Encoding.UTF8;
            }
            else if (ss[0] == 0xFE && ss[1] == 0xFF && ss[2] == 0x00)
            {
                reVal = Encoding.BigEndianUnicode;
            }
            else if (ss[0] == 0xFF && ss[1] == 0xFE && ss[2] == 0x41)
            {
                reVal = Encoding.Unicode;
            }
            r.Close();
            return reVal;

        }

        /// <summary> 
        /// 判断是否是不带 BOM 的 UTF8 格式 
        /// </summary> 
        /// <param name="data"></param> 
        /// <returns></returns> 
        private static bool IsUTF8Bytes(byte[] data)
        {
            int charByteCounter = 1;
            //计算当前正分析的字符应还有的字节数 
            byte curByte; //当前分析的字节. 
            for (int i = 0; i < data.Length; i++)
            {
                curByte = data[i];
                if (charByteCounter == 1)
                {
                    if (curByte >= 0x80)
                    {
                        //判断当前 
                        while (((curByte <<= 1) & 0x80) != 0)
                        {
                            charByteCounter++;
                        }
                        //标记位首位若为非0 则至少以2个1开始 如:110XXXXX...........1111110X　 
                        if (charByteCounter == 1 || charByteCounter > 6)
                        {
                            return false;
                        }
                    }
                }
                else
                {
                    //若是UTF-8 此时第一位必须为1 
                    if ((curByte & 0xC0) != 0x80)
                    {
                        return false;
                    }
                    charByteCounter--;
                }
            }
            if (charByteCounter > 1)
            {
                throw new Exception("非预期的byte格式");
            }
            return true;
        }

    }
}
